I have owned and used both the Shelter 501-II and Soundsmith SMMC1 cartridges your rig - Aries 1 and JMW10 arm. I was not fond of the 501-II stereo cartridge.JMW arm combination. It's not so much that it was bad, as there were other combinations that were so much better IMHO.
It's hard to compare the Soundsmith to the Shelter (or other LOMC carts) because of the difference in design and the additional circuitry in the chain (SUT in my case). Needless to say, I think that the SMMC1 is one of (if not the) best bargain in a new cartridge. Is it the best cartridge I have ever owned or tried? No, but it gets you very close to the ultimate, and having a more expensive cartridge requires you (or at least, me) to improve everything else in the chain to the point of economic unfeasability.
Knowing what I know now, if I still owned the Aries 1 I would order a pair of Soundsmith Zephyr cartridges; one for stereo and one for mono, and be done with it. But that's if it were me.